Foreign nationals residing in Japan who will temporarily leave Japan for any reason, such as for a family visit or vacation, must obtain a Re-Entry Permit. If you leave the country without obtaining a Re-Entry Permit, you will need to obtain a certificate of eligibility, a new visa, and a new alien registration card. You must take your alien registration card with you whenever you leave the country temporarily, because may be asked to present it when you come back in.
There are two types of Re-Entry Permit: single and multiple. The Re-Entry Permit is only valid for a maximum of the period for which your status of residence is valid.